Process for the conversion of soaps of unsaturated into soaps of saturated fatty acid



United States Patent Orifice PROCESS FOR CONVERSIQN QF SOAPS F UNSATURATED INTO SOAPS 0F SATURATED FATTY ACID Werner Stein, Dusseldorf-Holthausen, and Helmnt Hartmaim, Dusseldorf, Germany, assignors to Henkci & Cie. m. h. H., Dusseldorf-.Holthausen, Germany No Drawing. Application July 5, 1955, Serial No. 520,118

. C a ms- (C 60- The present invention relates to the treatment of alkali e l ans f unsatu a e a y add a d s a s mifi tion-in-part of our copending application Ser. No. 236,088, filed July 10, 1951.

More particularly, the invention relates to the conversion of these soaps into alkali metal soaps of saturated fatty acids.

Fats or mixtures of fatty acids having a high content of fatty acids with chain lengths from C12 to C16 are preferred in the preparation of washing agents because the agents so prepared have a particularly good lathering Power a d deterg n a t o Large a o n of fatty acids of S id chain length are found especially in a few a le f t n oi s. a f nstance coconu oi 0. vegetable and animal fats and oils contain fatty acids .Of higher chain lengths. Some of the naturally occurring fats and oils are highly unsaturated and are, therefore, less suitable for the preparation of washing agents.

In such fatty acids as are found particularly in the fats of marine animals, a degradation is possible by treatment with a large excess of anhydrous caustic alkalis at elevated temperatures.

When a quantitative degradation reaction is to occur, 1 mol acetic acid and 1 mol hydrogen are set free per double bond. The saturated fatty acids obtained by the degradation are in the form of their salts and they have a chain length which is 2 carbon atoms shorter per double bond than that of the acid used as starting material. This reaction has been known for a long time. For neutralizing the acetic acid obtained in the degradation, alkali is necessary in the stoichiometric amount of 1 mol caustic alkali per mol of the alkali salt of the fatty acid, and per double bond; that is to say: for working up 1 mol of the alkali metal salt of an unsaturated fatty acid with 1 double bond, 1 mol of caustic alkali is needed, whereas for working up an unsaturated fatty acid with 2 double bonds, 2 mols of caustic alkali are needed. For the complete degradation of alkali metal salts of un saturated fatty acids with multiple double bonds, correspondingly more caustic alkali is required.

In practice, the degradation of salts of unsaturated fatty acids has always been effected with a considerable excess above the theoretically necessary amount of caustic alkali required; this is a definite drawback of the known processes. The reaction proceeds considerably better when the expensive potassium compounds (potassium soaps and potassium hydroxide) are used than with the cheaper sodium compounds. Therefore, working with high excess of potassium hydroxide is a considerable economic problem which stood in the way of a practical realization of the process. Moreover, the large excess of caustic alkali in the soaps so obtained was a further drawback for practical purposes. Finally, the formation of unsaponifiable decomposition products and marked discoloration were disadvantages of the known processes which could not be avoided.

The invention now relates to an improvement of the known process for the degradation of soaps of unsatu- Pa ented Sept. 17, R357 rated fatty acids with formation of soaps of substantially saturated fatty acids, in which the disadvantages of the known processes are avoided. Following the process according to the invention which may be carried out in batches or continuously, the soaps of fatty acids which are practically free of resin soaps, are worked up in the presence of water at temperatures from 300-450 C. and at pressures of at least IOQ kg./ sq. cm.

When potassium soaps and potassium hydroxide are used, the reaction sets. in at temperatures of 300 C. with reaction velocities that make the process technically useful.

When sodium soaps and sodium hydroxide are used, it is advisable I0 operate at somewhat higher temperatures, e. g. at least 3 3l),350 C. When mixtures of the above named alkali hydroxides are used, the temperatures lie between those mentioned above in case one of the alkali hydroxides is used alone. However, it is preferable to work at temperatures lying between 350 and 430 C.

In carrying out the process, pressures of kg. per sq. cm. and higher are necessary in order to insure the presence of water in the reaction mixture during the entire reaction. The amount of water should be at least 20 percent by weight calculated on the fatty acid under treatment. When the soaps are made at the start of the reaction by neutra ization of the fatty acids with alkali hydroxide, the water obtained during neutralization should be considered in the computation of the water content. The water present in the reaction mixture while the reaction proceeds, which is indicated in the minimum amount, serves f r iql efying said mixture and for preventing the formation of unsaponifiable decomposition products. Water can be used in a considerably larger amount, for instance up to 5 times the weight of the fatty acid present in the form of soap. Preferably, 40-200 percent of water calculated on the fatty acid are used.

The working with Water as liquefying agent for the reaction medium presents a considerable technical advantage as compared to the known processes. In previous work, particularly in processing difiicultly melting sodium soaps, it has been customary to add parafiin oil as a liquefying agent; however, this had to be removed from the reaction mixture by laborious steps. When working according to the invention, this addition is dispensable.

When work is to proceed with sodium soaps in the absence of a larger amount of water, this is only possible when the fatty acid mixtures to be processed contain considerable amounts of resin soaps which allow a liquefaction of the mixture even in absence of water, due to their low melting points. The presence of resin soaps, however, is undesirable since it causes considerable discolorations, as is evidenced for instance in the case of tall oil soaps. As contrasted thereto, not only are .discolorations avoided when working according to the invention, but in some cases even a brightening of the fatty acids under treatment is obtained.

In the reaction mixture pressure should be maintained which prevent the reaction mass from boiling, i. e. the pressure should be at l ast equal to the saturation pressure of the water. This pressure will adjust itself automatically when the process according to the invention is carried out in a closed autoclave and the saturation pres sure is even exceeded due to hydrogen being evolved in the course of the reaction. In some cases, however, it is desirable to remove the hydrogen evolving during the reaction, in which case it is necessary to take care that the pressure will not drop below the saturation pressure of the water present in the reaction mixture. The minimum pressure to be observed during operation has been given as 100 kg./sq. cm. It is not necessary to indicate a maximum pressure since it adjusts itself, as mentioned above, according to the water content in mixture, the working temperature, the size of the reaction vessel, and the quantity of hydrogen evolved during the reaction process. The preferred pressures for carrying out the process are between 150 and 300 kg./sq. cm.

It is a particular advantage of the process according to the invention that the quantity of alkali needed in the reaction is very low; it amounts to 80200% of the stoichiometric quantity of alkali, necessary for working up the alkali metal soaps of unsaturated fatty acids. The theoretical amount can be calculated from the molecular weight of the fatty acids to be processed and the number 'of double bonds present per molecule, in the average.

Preferably, for practical purposes 100-125% of the stoichiometrically necessary amount of alkali is used.

As a reaction product, we obtain in this manner a soap with very low contents in free caustic alkali, which in some cases is even altogether absent. Such soaps are particularly useful for direct processing into washing agents. If desired, the alkali metal acetate formed during the reaction and contained in the reaction product may be eliminated for instance by salting out. For many technical purposes it is, however, not necessary to distill off the fatty acid, which is separated from the soaps by acidifying I and thereafter isolated.

All unsaturated fatty acids, no matter of what origin, may be used as starting materials for the process according to the invention, provided they do not contain any notable amount of resin acids. Principally used are naturally occurring unsaturated fatty acids, such as are obtained from plants, and landor marine animals. Fatty acids derived from the fats of the latter animals are of considerable importance since they are especially rich in unsaturated components. Due to their unpleasant odor and their highly unsaturated character, fatty acids obtained from these sources, or soaps made therefrom, were hitherto not suited for many purposes. These fats frequently contain large amounts of fatty acids with more than 18 carbon atoms per mol, the soaps of which are undesirable for washing agents. By the process according to the present invention the higher unsaturated fatty acids are converted into lower saturated fatty acids which, depending on the number of double bonds contained in the acids used as starting materials, contain 2, 4, or 6 C atoms less and have therefore a much better suited chain length as far as processing to washing agents is concerned.

In the following, the process according to the invention is illustrated in a number of examples in which preferred embodiments for carrying out the invention have been described in detail. It should, however, be understood that these are given by way of illustration and not of limitation and that many changes can be made in the details without departing from the spirit of the invention.

For carrying out the degradation operations, a soap of a fatty acid mixture containing unsaturated fatty acid was neutralized with aqueous caustic alkali solution in the reaction vessel and was heated to reaction temperature with alkali in the presence of water in a closed autoclave comprising a stirrer.

In most cases the autoclave remained closed until the reaction product had cooled down after termination of the treatment. Only in a few cases, in which the pressure generated during the reaction approached the maximum pressure for which the autoclave was built, so much gas was allowed to escape from the closed chamber that the maximum pressure was not exceeded. In these cases, the examples indicate how often and to what amount pressure was lowered when the gas was blown off. Afterthe autoclave heating had been shut off, the autoclave was allowed to cool down while closed and was only opened after the hydrogen formed during the reaction had been blown off. The reaction product was dissolved in an excess of hot water and the fatty acid was separated by the addition of dilute sulphuric acid. p 1

the reaction 'the autoclave was closed The acid aqueous layer was discarded and the obtained fatty acid was tested after washing with water and drying. The particular data for each test are recited in the following examples.

In Examples 1 to 7 the starting product was a technical olein having an I. V. of 85.7, an A. N. of 190, an S. V. of 195, and an F. P. below 0 C. V

The content of fatty acids of different chain lengths was as follows:

Percent C12 2.0 C14 5.5 C16 10.5 C18 69.5 C1s 12.5

In Examples 8 to 10, the starting material was a train oil fatty acid having an I. V. of 138, an A. N. of 191, an S. V. of 196 and an F. P. of 24.9 C.

The content of fatty acids of different chain lengths was the following:

Percent C14. 3.0 C16 21.0 C18 25.0 C20 19.5 C22 20.5 022 11.0

The starting material for the tests described in Exam ples 11 to 13 was a fatty acid of soybean oil havingthe following characteristics: 1. V.=l07; A. N.=200; S. V.=

Distribution of chain lengths 7 Percent C12 1.5 C14 2.0 C16 21.0 C18 68.0 C1s 7.5

The amount of the fatty acids of difierent chain lengths in the starting materials and in the obtained degraded fatty acids was determined by distilling the methylesters of the fatty acids in a fractionating column.

In the following examples the maximum pressures and pressures after cooling are given as separate items. When after blow-off, in most cases the maximum pressure was again reached. The number of blow-offs, if any, is indicated.

In the last line of each example caustic alkali indicates the amount of alkali in percent of the stoichiometrically necessary amount. In calculating the percentage figures, consideration was given to the fact that the alkali amounts used in the operations refer to technical caustic alkalis containing about of alkali hydroxides.

EXAMPLE .1 Batch: 300 g. of olein, 129 g. of caustic potash, 45 g. of water.

Fatty acid obtained: 1. V.=32; F. P.=41.9 C.; newly formed U. S. (unsaponifiable matter)=l.4%.

Distribution of chain lengths Percent C12 4.0 C14 14.5 C16 43.5 C13 a 27.0 C1a 11.0

a EXAMPLE 2 Batch: 340 g. of an anhydrous potassium soap from olein, 51 g. of caustic soda, 153 g. of water.

Data of reactions Time hour 1 Temperature C 385 Highest pressure". kg./sq. cm 188 Pressure after cooling kg./sq. cm 38 Caustic alkali 120 Fatty acid obtained: I. V.='31; F. P.=39.8 C.; newly formed U. 'S.=1.0%.

Distribution of chain length- I Percent C1z 2.0 C12 2.5 C14 13.5 C16 39.0 C13 27.5 C1a 15.5

EXAMPLE 3 Batch: 323 g. of an anhydrous sodium soap from olein, 71 g. ofcaustic potash, 153 g. of water.

Data of reactions Time hour 1 Temperature v, C..- 385 Highest pressure" kg./sq. cm 189 Pressure after cooling kgJsq. cm 34 Caustic alkali 119 Fatty acid obtained: I. V.=30; F. P.=39I5 C.; newly formed U. S.=1.5%.

Distribution of chain lengths.

Percent C12 1 .5 C12 7 a 4.0 C14 13.5 C16 38.5 C18 29.0 C1a 1 3.5

EXAMPLE 4:

Batch: 400 g, of olein, 172 g, of caustic potash, 180 g. of water.

Data of reactions Time "hours" 4 Temperature C 385 Highest pressure kg,/sq. cm 253 Pressure after cooling kg./ sq. cm 62 Caustic. alkali 1'13 Fatty acid obtained: I. V.=23; F. P.=43 C.; newly formed U. S.=3.0'%.

Distribution of chain lengths- Percent C12 ,v 2.0 C12 3.5 C14 15.5 C16 7 44.5 C18 I 20.0 C1s 14.5

EXAMPLE 5 Batch: 400 g. of olein, 110 g. of caustic soda, 180g. of water.

Data of reactions Time hours 4 Temperature C.. 385 Highest pressure. kgJsq. cm 225 Pressure after coo1ing kg./sq. cm 38 Blow-offs kgJsq. cm 2X Caustic alkali 91 Fatty acid obtained: 1 V.=30; F. 11:38.1 (3.; newiy formed U. .S.=3.0%.

Distribution of chain lengths Percent C12 2.0 C12 3.5 C14 14.0 C16 39.0 C18 24.5 C1a 17.0

EXAMPLE 6 Batch: 300 g. of olein, 92 g. of caustic soda, 270 g. of water.

Data of reactions Time h urs 4 Temperature I C 385 Highest pressure kg./sq. cm 240 Pressure after cooling kg./sq. cm 40 Caustic alkali Fatty acid obtained: I. V.=31-; F. P.=39.5 C.; newly formed U. S. 2.5%.

Distribution of chain lengths Percent C12 5.0 C14 13.5 C16 39.5 C18 29.0 C18 13 .0

EXAMPLE 7 Batch: 400 g. of olein, 123 g. of caustic soda, g.

of water.

1 Data of reactions Time hours 4 Temperature C 385 Highest pressure kg-./sq. cm 220 Pressure after cooling kg./sq. cm 50 Caustic alkali 114 Fatty acid obtained: I. V.=31; F. P.=-3'8.9 C.; newly formed U. S.=4%.

Distribution of, chain lengths Fatty. acid obtained: I. V.=28; F. P.=36.5 C.; newly formedU. S.=5.2%..

Distribution. of. chain lengths Percent C12 1.5 C12 3.0 C14 10.5 C16 28.5 C13 17.0 C20 14.0 C22 10.0 C22- I515 EXAMPLE 9 Data of reactions Time ours... 4 Temperature C 385 Highest pressure kg./sq. cm 220 Pressure after co ng ks! lsq. cm 43 Blow-oils kgJsq. cm 1X10 Caustic alkali 110 Fatty acid obtained: 1. V.= 17; F. P.=40.1 C.

7 Distribution of chain lengths Percent C12 1.0 C12 3.0 C14 13.5 C16 32.5 C13 19.0 C20 17.0 C22 '7.5 C22 6.5 EXAMPLE Batch: 400 g. of train oil fatty acid, 112 g. of caustic potash, 80 g. of caustic soda, "180 g. of water.

i V 7' 7 Data of reactions 7 V Time I hours" 4 Temperature C..- 385 Highest pressure ..kg./sq. cm 165 Pressure after cooling k g./sq. cm 52 V Caustic alkali 110 Fatty acid obtained: I. v.=19; F. r.==39 c.

- 7 Distribution of chain lengths a V 7 Percent C1 2 3.5 C12 g 3.0 C14 V 12.0 Cis 32.5 C18 18.0 C20 16.5 C22 9.0 C22 j5.5

. 1 EX P E 1 Batch: 300 g. of soybean oil fatty acid, 104 g. of caustic soda, 300 g. of water.

Data "of reactions Time hours 2 Temperature C 385 Highest pressur k lsq. cm 230 Pressure after cooling ;.kg'./sq. cm 28 Blow-ofis ';kg./sq. cm 3X20 Caustic alkali w 7 =108 Fatty acid obtained: I. V.=19; F. P.=38.1 C; newly formed U. S.=1.9%. N

' Distribution of chain lengths 1 Percent Ci2 H 1.5 C12 7 2.8 C14 28.2 C16 30.2 C18 18.7 C1s 18.6

' EXAMPLE 12 7 Batch: 300 g. of soybean oilfatty acid, 145 g. of caustic potash, 300 g. of water. n

Data of reactions V alkali used is caustic soda solution.

Temperature C 385 Highest pressure kg./sq. cm 242 Pressure after cooling "kg/sq. cm 42 Blow-offs kg./ sq. cm 1 X32; 1 X 10 Caustic alkali 108 Fatty acid obtained: 1. v =19; F. P.=38.4 0.; newly formed U. S.=4.1%. I

Distribution of chain lengths Percent 12 1.5 C12 3.5 C14 27.5 C16 32.0 C18 20.0

EXAMPLE 13 Batch: 3000 g. of soybean oil fatty acid, 1050 g. of caustic soda, 3000 g. of water.

' Data of reactions Time minntes 30 Temperature C 400 Highest pressure kg./sq. cm 287 Pressure after cooling kg./sq. cm 23 Blow-ofi kg lsq. cm 1X37 Caustic alkali 108 Fatty acid obtained: 1. V.=21; F. P.=38.9 C.; newly formed U. s.=1.s%.

Distribution of chain lengths What we claim is:

1. A process for converting unsaturated fatty acids into saturated fatty acids which comprises reacting alkali metal .soaps of said unsaturated fatty acids with a caustic alkali solution in the presence of water at temperatures ranging from 300-450 C., maintaining in the reaction vessel during the reaction a pressure of at least 100 kg./sq. cm., and using causti alkali in an amount of 200% of the stoichiometrically necessary amount.

2. A process according to claim 1 wherein the caustic 3. A process according to claim 1 wherein the caustic alkali used is caustic potash solution.

4. A process according to claim 1 wherein a mixture of sodium hydroxide and potassium hydroxide solutions are used.

5. A process according to claim 1 wherein the temperature used in the reaction ranges from 350-400 C.

6. A process according to claim 1 whereinthe pressure is maintained at 150-300 kg./sq. cm.

7. A process according to claim 1 wherein the amount of caustic alkali used is -125% of the theoretically necessary amount.

8. A process according to claim 1 wherein the amount of water present is 20500% calculated on the fatty acids to be converted. a

9. A process according to claim 1 wherein the amount of water present is 40200% calculated on the fatty acids to be converted.

2,481,356 Sept. 6, 1949 75 dnstry, March 29, 1883, pages 98101. 

1. A PROCRSS FOR CONVERTING UNSATURATED FATTY ACIDS INTO SATURATED FATTY ACIDS WHICH COMPRISES REACTING ALKALI METAL SOAPS OF SAID UNSATURATED FATTY ACIDS WITH A CAUSTIC ALKALI SOLUTION IN THE PRESENCE OF WATER AT TEMPERATURES RANGING FROM 300-45*C., MAINTAINING IN THE REACTION VESSEL DURING THE REACTION A PRESSURE OF AT ALEAST 100KG,/SQ,CM., AND USING CAUSTIC ALKALI IN AN AMOUNT OF 80-200% OF THE STOICHIOMETRICALLY NECESSARY AMOUNT. 